limit to 4 windows, and disable 'new window' menu item when that amount is reached

src/frontend/qt_sdl/EmuInstance.cpp

@@ -203,6 +203,12 @@ void EmuInstance::createWindow()
     // if creating a secondary window, we may need to initialize its OpenGL context here
     if (win->hasOpenGL() && (id != 0))
         emuThread->initContext(id);
+
+    bool enable = (numWindows < kMaxWindows);
+    doOnAllWindows([=](MainWindow* win)
+    {
+        win->actNewWindow->setEnabled(enable);
+    });
 }
 
 void EmuInstance::deleteWindow(int id, bool close)
@@ -232,6 +238,14 @@ void EmuInstance::deleteWindow(int id, bool close)
         // if the main window is closed, Qt will take care of closing any secondary windows
         deleteEmuInstance(instanceID);
     }
+    else
+    {
+        bool enable = (numWindows < kMaxWindows);
+        doOnAllWindows([=](MainWindow* win)
+        {
+            win->actNewWindow->setEnabled(enable);
+        });
+    }
 }
 
 void EmuInstance::deleteAllWindows()

src/frontend/qt_sdl/EmuInstance.h

@@ -28,7 +28,7 @@
 #include "Config.h"
 #include "SaveManager.h"
 
-const int kMaxWindows = 16;
+const int kMaxWindows = 4;
 
 enum
 {
@@ -87,6 +87,7 @@ public:
     melonDS::NDS* getNDS() { return nds; }
 
     MainWindow* getMainWindow() { return mainWindow; }
+    int getNumWindows() { return numWindows; }
     MainWindow* getWindow(int id) { return windowList[id]; }
 
     void doOnAllWindows(std::function<void(MainWindow*)> func, int exclude = -1);